1. Field of the Invention
The present invention relates to an auto focusing device for a camera and a method used in the auto focusing device for the camera for determining whether or not to emit an auxiliary light, and in particular, to an auto focusing device for a camera which detects a focus by emitting an auxiliary light to an object if the focus cannot detected.
2. Description of the Related Art
A large number of techniques are known with which if a focus cannot be detected, an auxiliary light is emitted to an object to detect the focus.
For example, with what is called single auto focusing, once the camera is focused, a focus detecting operation is locked. With this technique, an auxiliary light may be emitted if the results of the last auto focusing indicate that the focus cannot be detected owing to a low luminance. However, with what is called continuous AF which continuously performs a focus detecting operation after focusing or AF used for what is called continuous image taking in which images are continuously taken, when an auxiliary light similar to that used in the single AF is emitted, the light may become too intense depending on conditions for the object. That is, during the continuous AF or continuous image taking, when light emission control is performed which is similar to that used for the signal AF, the auxiliary light may be too glaring or batteries may be significantly consumed.
In view of these circumstances, various proposals have been made for auxiliary light emission control used for the continuous AF or continuous image taking.
For example, Jpn. Pat. Appln. KOKAI Publication No. 63-172226 proposes a technique to prohibit emission of an auxiliary light in a continuous image taking mode. Further, Jpn. Pat. Appln. KOKAI Publication No. 63-172227 proposes a technique to switch an AF mode to a single AF mode when an auxiliary light is emitted in a continuous AF mode. Moreover, Japanese Patent No. 2713870 proposes a technique with which once the camera is focused in the continuous AF mode, emission of an auxiliary light is prohibited during subsequent AF operations.